Rectifier system



Nov. 7, 1933. F, TERMAN 1,933,773

RECTIFIER SYSTEM Filed Dec. 23, 1929 INVENTOR. EFmDM/IQK 5, gwma/w,

' ATTORNEY 1 20 to be rectified is impressed across the plate andmission.

Patented Nov. 7, 1933 I UNITED STATES. mm

RECTIFIER SYSTEM Frederick E. Terman, Stanford University; Calif.,assignor to Wired Radio, Inc., New York, N. Y., a corporation ofDelaware Application December 23, 1929 Serial No. 416,173

9 Claims. (Cl. 250-27) My invention relates broadly to electron tubestructureis one important controlling condition rectifiers and moreparticularly to an inverted in this respect, and such operation isfacilitated electron tube circuit arranged to operate as a if theincoming signal is weak. The operation rectifier. will be betterunderstood by reference to Fig. 6

One of the objects of my invention is to pro of my Patent No. 1,846,0i3, which shows a com- 60 vide an improved rectifier circuit having astepplete static characteristic curve of grid current down voltagecharacteristic whereby relatively plotted against plate voltage. Theenergy to be large potentials of alternating characteristic rectified isimpressed across the plate and cathmay be impressed across the rectifiercircuit for ode electrodes while the rectified energy is dederiving arectified current of relatively small rived in the circuit connectingthe grid and 65 amplitude, cathode electrodes. The step-down voltageAnother object of my invention is to provide ratio obtainable in theelectron tube system is a rectifier or detector circuit which may besubdependent upon the structure and design of the jected to relativelylarge potentials for obtainelectron tube employed. In my copending apingstabilized rectifier or detector operation with- .plication Serial No.413,555, filed December 12, 70 out reaction due to the relatively largeI im 1929,.entitled Electron tubal have illustrated pressed potential.certain constructions. of electron tubes which A further object of myinvention is to promay be employed in the circuit arrangement of vide asystem of rectification wherein the energy my invention to secure thedesired voltage transcathode electrode of a three element tube and InFig. 1, I have illustrated a modified form the rectified energy derivedin an output cirof circuit arrangement embodying my invention cuitconnected to the grid and cathode elecwherein a highresistance leak pathis protrodes of the electron tube system. vided in series with the plateelectrode of, the

5 Other and further objects of my invention electron tube system whichincludes electron 80 reside in the circuit arrangement for an electube 1having cathode 2, grid electrode 3 and tron tube rectifier set forthmore fully in the plate electrode i. The cathode is heated fromspecification hereinafter following by reference battery system 5. Theoutput circuit includes to the accompanying drawing, wherein: battery 6having one terminal thereof directed 3 Figure 1 illustrates one form ofrectifier systoward the grid electrode 3 in such manner that tomembodying the principles of my invention; through the output load apositive bias and Fig. 2 illustrates a modified circuit arrangeismaintained on the grid 3. In series with'the ment for the rectifiersystem of my invention. plate circuit there is disposed a condenser '7In the circuits of my invention I employ the shunted by the highresistance leak path 8 by 35 principle of the inverted electron tube asset which the energy to be rectified is supplied to go forth more fullyin my copending application the plate electrode {l and in circuit withcathode Serial No. 405,363, filed November 7, 1929, now 2. The inputcurrent ficwingin the plate cir- Patent No. 1,846,043, issued February23, 1932, cult must pass through this condenser unit and and entitledElectron tube circuit. The input produces a d rect current voltage dropbetween 40 system for the electron tube employed in my cathode and platewhich iseffective in varying 95 invention connects between the plate andcaththeelectric field between cathode and grid, and ode electrodes whilethe output system in the hence varies the output current delivered bythe electron tube of my invention connects between grid. The energy tobe rectified is supplied the grid and cathode electrodes. The-plateelecacross the leads designated at 9. The rectified i5 trode may benormally'maintained at negative energy is delivered acrossthe'leadsdesignated 1 0 potential while the grid electrode is normally at 10.Rectification may be said'to occur in the maintained at positivepotential. It is also posplate circuit or input circuit. Therectification sible to operate the system of my invention withoccursbecause the characteristic curve of plate out applying a direct currentbiasing voltage to current against plate voltage is not linear.

the plate since the characteristic curve of an Since grid 3 ismaintained at a potential posi- 5 inverted three electrode tube showinggrid curtive with reference to cathode 2, adirect current rent plottedagainst plate voltage shows a very 'will flow from cathode- 2 throughsource. 6, sharp peak at the point'of zero plate voltage. through load10, and to grid 3. The electron Conditions should beso maintained thatsubflow between cathode and grid .Will be varied stantially no platecurrent will flow; the tube by the variations in the electric fieldbetween. 11

cathode and grid caused by the variations in the input potentialimpressed between plate and cathode. The current flowing to the positivegrid depends upon the electric field existing between cathode and grid,and is substantially independent of how this field is produced. Both thegrid and plate potentials affect the magnitude of this field.

In Fig. 2 I have shown an arrangement of rectifier circuit in which theinput system includes biasing battery 12 for normally maintaining theplate 4 at negative potential. Relatively high potentials impressedacross the circuit 9 are rectified and producerelatively low rectifiedcurrent at the terminals 10 for distribution to the load.

No current fiows in the plate circuit because the plate is negativelybiased. This bias should be adjusted to the portion of thecharacteristic curve of suitable curvature. The alternating voltageimpressed between plate and cathode will vary the electric field betweenplate and cathode, including the electric field between grid andcathode, and hence will vary the output current delivered by the grid. Ihave usually found greater sensitivity by employing the condenser andleak in the plate circuit with little or no plate bias. The higher theresistance of the plate leak, the more sensitive the detection.

In both forms of the circuits as described, the direct current outputderives its essential energy from the gridbattery 6. The direct currentflowing in the grid circuit is, however, varied or controlled inaccordance with the alternating voltage impressed between plate andcathode. The type of rectification obtained by the arrangements shown inFigs. 1 and 2 is analogous to the rectification obtained in the normaltype of detector circuit with the usual three electrode tube applyingthe input to the grid and delivering output from the plate...

Fig. 1 corresponds to the ordinary type of grid-leak grid-condenserdetection with normally operated tube in which the applied signalvoltage is rectified by the non-linearity of the grid-filament circuit,producing a rectified grid current that must fiow through the grid-leakgrid-condenser impedance and produce a voltage drop, which in turnaffects the plate current o'i' the tube by ordinary amplifier action, asdescribed in my paper which appeared in the October 1928 issue of theProceedings of the Institute of Radio Engineers, vol. 16, page 1384.

Fig. 2 corresponds to the usual type of detector circuit with normallyoperated tube employing a negatively biased grid battery whereinrectification may be said to occur in the output or plate circuit. Inthe system of my invention, particular methods are employed for applyingthe inverted electron'tube to detector circuits heretofore known withnormally operated tubes having input connected to the grid and outputconnected to the plate. It should be particularly noted that in thesystem of my invention, no substantial portion of the output energy isderived from the alternating current input but that substantially all ofthe output energy is derived from the grid battery 6. In the invertedvacuum tube system of my invention, an alternating current applied tothe plate has the same effect on the output or grid current as though apotential of similar wave form but much less voltage had instead beenadded to the grid batshown in Fig. 2, rectification takes place in theoutput or grid circuit.

In leak condenser rectification, as shown in Fig. 1, the rectificationresults from the nonlinear relation that exists between the platecurrent and the plate voltage when the plate poten tial is at or nearzero volts with respect to the cathode. With detection of this type, therelationship between positive grid voltage and grid current ispreferably linear. Leak condenser rectification always takes place witha grid current which increases as the voltage being rectified becomesgreater. In contrast with this anode current rectification with theinverted tube makes use of the non-linear relation that exists betweenanode current and anode voltage when the plate is biased with arelatively high negative potential that approaches the cut-offcondition. Anode rectification of this type takes place entirely in theanode circuit and is not accompanied by the presence of grid currentunless the rectifier is overloaded. Anode rectification can only takeplace when the operating conditions are such that the anode current andanode voltage have a non-linear relation.

While I have described the rectifier and detector circuits of myinvention in certain preferred embodiments, I desire that it beunderstood that modifications may be made and that no limitations uponmy invention are intended other than are imposed by the scope of theappended claims.

What I claim as new and desire to secure by Letters Patent oi the UnitedStates is as follows:

1. In a rectifier circuit an electron tube including cathode, grid and,plate electrodes, an input circuit connected across said plate andcathode electrodes, an output circuit connected across said grid andcathode electrodes, a source of energy connected for applying a positivepotential to said grid with respect to said cathode, and means connectedin circuit with said plate electrode for determining the operation ofsaid electron tube as a rectifier whereby potentials supplied acrosssaid plate and cathode electrodes for charging said grid electrode atpositive po-' tential whereby relatively high potentials impressedacross said input circuit are stepped down, rectified, and the rectifiedcurrent delivered at lower amplitude to said output circuit.

tube including cathode, grid and plate electrodes, an input circuitinterconnecting said plate and cathode electrodes, an. output circuitinterconnecting said grid and cathode electrodes, meansfor maintainingSaid grid electrode at positive" potential, and a reactance connected incircuit with said plate electrode in said input circuit wherebyrelatively high potentials impressed across said input circuit arestepped down, rectified and the rectified current of relatively lowamplitude delivered to said output circuit.

4. In an inverted electron tube rectifier system, an electron tubehaving at least one cathode, one grid, and one plate, a source ofalternating cur- 3. A rectifier system comprising an electron rent to berectified connected to said plate and said cathode, a source of directcurrent grid potential, and an output circuit connected through saidsource of grid potential to said grid and said cathode for applying tosaid grid a potential positive with reference to said cathode.

5. In an inverted electron tube rectifier system, an electron tubehaving at least one cathode, one grid, and one plate, a source ofalternating ciu'rent to be rectified connected to said plate and saidcathode, means connected in series between said source and said plateand cathode for maintaining said plate at a determined potential withreference to said cathode, a source of direct current grid potential,and an output circuit connected through said source of grid potential tosaid grid and said cathode for applying to said grid a potentialpositive with reference to said cathode.

6. In an inverted electron tube rectifier system, an electron tubehaving at least one cathode, one grid, and one plate, a source ofalternating current to be rectified connected to said plate and saidcathode, a condenser connected in series between said source and saidplate and cathode, a high resistance connected in shunt with saidcondenser, a source of direct current grid poten tial, and an outputcircuit connected through said source of grid potential to said grid andsaid cathode for applying to said grid a potential positive withreference to said cathode.

7. In an inverted electron tube rectifier system, an electron tubehaving at least one cathode, one grid, and one plate, a source ofalternating current to be rectified connected to said plate and saidcathode, a source of'directcurrent powith respect to said cathode,asource of direct current grid potential, and an output circuitconnected through said source of grid potential to said grid and saidcathode for applying to said grid a potential positive with reference tosaid cathode.

8. In a rectifier system employing a three electrode electron tube, themethod of rectification which consists in applying the voltage to berectified between the plate and cathode of said tube, maintaining saidplate at a negative potential with reference to said cathode,maintaining said grid at a positive potential with reference to saidcathode, and delivering the output of said system from said grid andsaidcathode.

9. In a device of the class described, an electron tube having at leastthree electrodes, namely a plate, a cathode and a grid, an input circuitconductive of alternating potentials and connected between said plateand said cathode, an output circuit including a source of energy forpositively biasing said grid with respect to said cathode and connectedbetween the two electrodes last mentioned, and meansincluding thestructural arrangement of said electrodes and the provisicnof azero-bias applied to said plate with respect to said cathode for causingsaid alternating potentials to produce a rectifying control of thecurrents in said output circuit.

FREDERICK E. TERMAN.

